DE 10 2004 002 061 A1 has disclosed a method for control and regulation of a drive train of a hybrid vehicle and a drive train of a hybrid vehicle. With the method for control and regulation of a drive train of a hybrid vehicle having an internal combustion engine, an electric engine, a shifting element located between the electric engine and an output in a power flow of the drive train and a shifting element designed with continuously variable transmitting capacity and a clutch device situated between the electric engine and the internal combustion engine and by way of which the electric engine and the internal combustion engine can be brought to operative connection, a drive train of a hybrid vehicle be operable in a manner such that a transition from a drive of the hybrid vehicle by the electric engine to a parallel drive of the hybrid vehicle via the electric engine and the internal combustion engine or to a pure drive on the side of the internal combustion engine of the hybrid vehicle, the same as a starting operation of the internal combustion engine via the electric engine, can be carried out without reaction torques on the drive train side noticeable for the driver of the hybrid vehicle.
In the operation of the drive train, the transmitting capacity of the shifting element can be adjusted for the purpose during a starting process of the internal combustion engine so that on the output of the drive train abuts a torque independent of a starting process of the internal combustion engine, there being prevented on the output, preferably by a slip operation of the shifting element, torques appearing on the output as result of the starting of the internal combustion engine.
In the method, the rotational speed of the electric engine during the starting phase of the internal combustion engine is raised to a rotational speed value at which is ensured that during the whole starting process of the internal combustion engine, the shifting element between the electric engine and the output of the drive train be kept in a slip operation. The rotational speed value is calculated via an algorithm implemented in the engine control and/or in the transmission control and/or in a superimposed torque manner.
However, it is here disadvantageous that the calculated rotational speed value, under operating conditions that change during the starting process of the internal combustion engine, is in circumstances too low and the shifting element is not slip operated over the whole starting process of the internal combustion engine. It is further possible also that the rotational speed value of the rotational speed of the electric engine determined for the operating state existing at the calculation moment be basically too high for the operating states of the drive train that follow wherefore a load of the shifting element caused by the slip in the area of the shifting element assumes undesirably high values.
Therefore, the problem on which the instant invention is based is to make available for operating a parallel hybrid drive train of a vehicle a method by means of which a shifting element between an electric engine and an output of a vehicle can be slip operated during the whole starting process so as to make possible preventing on the output side of the drive train reactions that diminish the driving quality, the same as inadmissibly high loads for the shifting element.